Balance weight attachment for turbine wheels

ABSTRACT

A balance weight attachment for use in the balance groove of a turbine wheel wherein the necessity of an access slot for inserting the balance weight attachment is obviated. The balance weight attachment is formed so that it may be inserted anywhere along the balance groove and then locked in place by a screw adjustment which loads against the side of the groove.

[451 June 5, 1973 2,958,165 11/1960 Hofmann...........................74/573 X FOREIGN PATENTS OR APPLICATIONS [54] BALANCE WEIGHTATTACHMENT FOR TURBINE WHEELS 24,573 3/1912GreatBritain..........................51/169 Schenectady,

[75] Inventor: Richard A. Neary,

General Electric Company, Primary Examiner-Charles J. Myhre AssistantExaminer-F. D. Shoemaker [73] Assignee:

Schenectady, NY.

Attorney William C. Crutcher and James W. Mitchell [22] Filed: Aug. 19,1971 ABSTRACT [2l] Appl. No.: 173,101

A balance weight attachment for use in the balance U S Cl 74/573 416/144416/215 groove of a turbine wheel wherein the necessity of an accessslot for inserting the balance weight attachment is obviated. Thebalance weight attachment is formed so that it may be inserted anywherealong the balance groove and then locked in place by a screw adjustmentwhich loads against the side of the groove.

...Fl6f 15/32 [51] Int. Cl.

Field of Search [56] References Cited UNITED STATES PATENTS 3 Claims, 5Drawing Figures 2,957,366 10/1960 Driveretal...........................74/573 BALANCE WEIGHT ATTACHMENT FOR TURBINEWHEELS BACKGROUND OF THE INVENTION This invention relates in general towheel balancing, and in particular to balancing a turbine unit rotor bymeans of a weighted insert.

In the manufacture of turbo-machinery, if excess vibration is to beavoided, it is necessary that all rotating parts be balanced to withinseveral inch grams. Turbine wheels are sometimes formed with an annulardovetail groove located within the balance plane and hence called abalance groove. Weights are inserted into the dove-tail balance groovethrough either one of two oppositely situated access slots, and then arepositioned by sliding the weights around the balance groove. When theproper balance is achieved, the weights are secured within the balancegroove.

Sometimes, due to necessities of construction, obstructions such asrotor bolts are circumferentially arranged in the balance groove pathcausing interruptions in the balance groove, therefore obstructing thesliding of weights into place and requiring that the weights be insertedat the point of balance. It is then required to have available a weightwhich can be inserted at the point of balance without the aid of anenlarged access slot in the dovetail balance groove.

One solution is the use of split weights hereinafter described. The useof split weights has been generally satisfactory but the possibility offailure and consequent damage has required a search for a new way ofinserting the balance weights.

OBJECTS OF THE INVENTION Accordingly, it is one object of the presentinvention to provide an improved balance weight attachment.

Another object of the invention is to provide an improved balance weightattachrnent which will obviate the necessity of an access slot withinthe dovetail balance groove.

Another object of the invention is to provide a onepiece balance weightto replace the split weight device.

Finally, it is an object of this invention to provide a universalbalance weight attachment which will be suitable for both continuous andinterrupted balance grooves.

Other objects, advantages and features of the present invention willbecome apparent from the following description of the preferredembodiment thereof when read in connection with the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevation view of aturbine wheel with an uninterrupted balance groove.

FIG. 2 is .a cross section view of a balance groove taken along IIII ofFIG. 1 having the conventional prior art balance weight insertedtherein.

FIG. 3 is a front elevation view of a turbine wheel with an interruptedbalance groove.

FIG. 4 is a cross-section view of a balance groove taken along IV-IV ofFIG. 1 having the prior art split weight balance weight insertedtherein.

FIG. 5 is an enlarged cross-section view of a balance groove of the typeshown in either FIG. 1 or FIG. 3 having the present invention appliedthereto.

SUMMARY OF THE INVENTION A one-piece balance weight attachment for aturbine wheel wherein the balance weight may be inserted into a balancegroove without an access slot. The balance weight is formed so that itmay be inserted any place around the annular balance groove. One side ofthe balance weight is formed with a projection which bears against oneside of the balance groove while the body portion of the balance weightis formed with an oblique threaded hole into which a fastener isinserted until it engages the other side of the balance groove.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the accompanyingdrawings, FIG. 1 discloses a turbine rotor generally shown at 11comprised of a shaft portion 13 and a wheel portion 15. An annulardovetail groove 17 or similar groove which is narrower at the top thanat the bottom is cut into the wheel face and is formed with oppositelydisposed, enlarged access slots 21. The slots are usually oppositelydisposed and formed in pairs because it is desired to maintain the wheelbalance, although one slot is sufficient for the purpose of mountingbalance weights into the balance groove.

A conventional balance weight 25 is disclosed in FIG. 2 and is comprisedof two side projections 27 which may engage either side of the balancegroove, and a vertical threaded hole 29 into which a screw 31 isinserted. The screw is tightened, causing the balance weight to loadagainst the sides of the groove. The screw itself is turned against thebottom of the groove. The balance weights are inserted in pairs so as toprovide a fine adjustment when balancing.

FIG. 3 shows a turbine wheel including an interrupted balance groove 35.A number of circumferentially spaced bolts 37 are arranged in the groovepath so that the use of a single pair of access slots would beineffective. Therefore, it becomes necessary to insert the balanceweights into the balance groove without the use of the slots.

A split weight 41 as shown in FIG. 4 has been devised in the prior art,comprised of two halves, each having a side projection 43. The twohalves are rejoined once inserted into the dovetail groove at a seam 45as the screw 47 in the threaded hole 49 is tightened against the bottomof the groove.

The present invention obviates the necessity of the split weightconstruction by providing a single body portion 51 mounted in a groove53 which may represent either an interrupted or uninterrupted balanceweight groove. One side of the body portion may be formed with aprojection 55 which may bear against one side of the groove while theother side of the body portion is formed with a generally flattenedsurface 57.

A threaded oblique'passageway 61 is cut into the body portion so that aset screw 65 may be passed therethrough so as to bear against the otherside of the groove when the screw is tightened. This will cause thebalance weight to be secured within the groove.

In operation, the balance weights are inserted into the dovetail grooveprojection side first and then secured by screws. Removal isaccomplished by loosening the screw and then withdrawing the balanceweight, flattened side first, from the groove.

While this invention has been generally discussed in terms of usingscrews as the fastening means for the balance weight, it should beappreciated that other types of fasteners may also be be employed.

While there is shown what is considered to be the preferred embodimentof the invention, it is of course understood that various othermodifications may be made therein, and it is intended to cover in theap-' pended claims all such modifications as fall within the true spiritand scope of the invention.

What is claimed is:

1. A balance weight attachment for a wheel, the wheel having an annulardovetail groove formed thereon defined by a pair of opposing slopingsides and a base; said balance weight attachment comprising:

a body portion having a projection thereon defining an inclined surfacesubstantially conforming to a the inclined surface.

1. A balance weight attachment for a wheel, the wheel having an annulardovetail groove formed thereon defined by a pair of opposing slopingsides and a base; said balance weight attachment comprising: a bodyportion having a projection thereon defining an inclined surfacesubstantially conforming to a portion of one Of said dovetail sides; thebody portion also including an oblique passageway therethrough anddirected toward the opposite side and base of said dovetail groove; and,fastening means inserted in said passageway and disposed to load againstthe opposite side and base of said groove.
 2. The balance weightattachment as recited in claim 1 wherein the oblique passageway is athreaded hole and the fastening means is a set screw.
 3. The balanceweight attachment according to claim 1 wherein the body portion is flaton the side opposite the inclined surface.